Warfarin

Specimen:

5 mL blood in EDTA tube.

Method:

HPLC.

Application:

Documentation of accidental or intentional overdose (including some rat poisons).

This test is not used for monitoring warfarin therapy; see INR.

Occasionally helpful to document lack of compliance with warfarin therapy or surreptitious use of the drug.

Interpretation:

The presence of warfarin indicates ingestion has occurred.

Reference:

Kelly JC and O’Malley K. Clin Pharmacokinet 1979; 4: 1-15.